Preparation of amides



Patentecl May 26, 1953 UNITED STATES PATENT OFFICE PREPARATION OF AMIDESNo Drawing. Application March 9, 1951, Serial No. 214,857

14 Claims.

This invention relates to the preparation of alkanoic acid amides; moreparticularly, it relates to a process for the preparation of amides fromorganic sulfides.

It has recently been reported in USP 2,495,567 to Carmack et al., thatamides are obtainable by reaction between olefinic compounds and aqueousammonium polysulfide. The reaction involved is similar to the reactiondiscovered by Willgerodt in 1887 at which time Willgerodt disclosed thereaction between aryl alkyl ketones and ammonium polysulfide to formnitrogeneous mate rials.

Copending application U. 8. Serial No. 185,907, filed September 20, 1950in the name of M. A. Naylor, Jr., now abandoned, describes and claims aprocess of reacting an alkene with ammonium polysulfide to produce analkanoic acid amide and an alkene-sulfur oil, separating the amide fromthe alkene-sulfur oil, and thereafter reacting the oil with aqueousammonium polysulfide to form additional alkanoic acid amide. Generally,in the reaction of an alkene with aqueous ammonium polysulfide, theformation of oils occurs at temperatures below 260 C. The oils generallycontain dialkyl sulfides, the sulfur content of which depends to someextent upon the amount of free and combined sulfur initially present inthe reaction mixture. Dialkyl monosulfide, dialkyldisulfide, and highersulfides of the dialkylpolysulfide type are thus obtainable, and areincluded in the oil mixtures. All of these oils are convertible toamides by reaction with aqueous ammonium polysulfide. The presentinvention, however, is directed to preparing alkanoic acid amides fromorganic sulfides without further addition of free or combined sulfur.

An object of this invention is to provide a process for obtaining amidesfrom organic sulfides, especially those of the formula (CnH2n+1)2srwherein a: has a value of at least 3. A still further object is toconvert alkene-sulfur oils to amides without the use of additionalsulfur. Other objects of the invention will appear hereinafter.

The aforesaid objects are accomplished in accordance with this inventionby heating an alkene-sulfur oil containing at least suiTcient sulfur tohave an average composition (C-nH2n+1) 283, with water and anitrogen-containing compound from the group consisting of ammonia,aliphatic primary amines and aliphatic secondary amines, at atemperature between 175 C. and

350 0., whereby the alkene-sulfur oil is con-' verted to an alkanoicacid amide, and thereafter separating the alkanoic acid amide from theresulting mixture. If water is omitted corresponding thioamides areformed.

In more specific form the reaction is carried out by heating analkene-sulfur oil having an average composition between (C'nHznHMSs and(CnH2n+1) 2S8, with ammonia and water at a temperature between 240 C.and 270 C. The value of n may vary quite widely since the size of thealkyl groups is not critical.

The alkene-sulfur oil's employed in the present invention may beprepared by several methods. An alkene may be reacted with sulfur in anaqueous or anhydrous medium at a temperature between C. and 250 0.,preferably between C. and 210 C. This reaction is facilitated by addinghydrogen sulfide to the initial reactants. Alternatively, analkene-sulfur oil may be prepared by reacting an alkene with sulfurdioxide and hydrogen sulfide in the presence of a catalytic amount of acompound from the group consisting of aliphatic tertiary amines, cobalt,nickel, zinc and manganese sulfides. This reaction is also carried outat a temperature between 160 C. and 250 C., preferably between 190 C.and 210 C.

In preparing the alkene-sulfur oil any aliphatic alkene may be employedin the aforesaid process, but particularly advantageous results areobtained when the alkene is propylene or isobutylene; the amidesproduced from these specific olefins are propionamide and isobutyramide,respectively. Other suitable alkenes include ethylene, n-butenes,pentenes, hexenes, 3,5,5-triinlfthylhexenes, dodecenes, octadecenes andthe The present invention resides in the discovery that thealkene-sulfur oils employed may be converted to an alkanoic acid amideby reaction with a nitrogen compound from the group consisting ofammonia, aliphatic primary amines and aliphatic secondary amines withoutfurther addition of free or combined sulfur. Hence, by completelyconverting an alkene to an alkene-sulfur oil, 1. e., a polysulfide oil,and thereafter converting the oil to amide in accordance with thepresent invention, exceptionally high conversion of alkene to thecorresponding alkanoic acid amide is obtained.

The following examples, in which all parts are by weight unlessotherwise specified, illustrate the present invention.

Example 1.-The following ingredients were introduced into a stainlesssteel cylindrical pressure tube:

Water (3.0 mols) -ffi Hydrogen sulfide (2.0-7 mols) 73.5 Sulfur dioxide(0.83 mol) 53 Trimethylamine (0.1 mol) 59 Propylenefl mol)-g 42 The tubewas shaken mechanically while heated to a temperature of 195-205 C. forminutes, and then cooled to room temperature. The gaseous products werereleased and the residual two-phase red brown liquid was filtered,removing 21.3 parts of suspended solids which was largely sulfur. Thepropylene-sulfur oil, which separated from the water solution, wasobtained as a dark red liquid consisting of about 114 parts, n =l.6313.'I'hepropylene-suliur oil contained 66.9% sulfur, 28.9% carbon and 5.55%hydrogen, corresponding to an average'composition of (C3.0H7.o) 2S5.2,was obtained in 90.1% conversion from propylene.

The approximate composition of the propylenesulfur oil determined bydistillation was as follows:

Per-cent nand isopropyl mercaptansruae s a 0.5

at 150 C. at 1 mm. pressure) Remainder The following materials wereintroduced into a stainless steel cylindrical pressure tube:

Parts Propylene-sulfur 011 (0.356 mol) (containing The tube was shakenmechaiiicallyand heated to245-'5 C. for 15rnmutesand(vaginal-tooled toroom temperature. Gaseous product's (largely-l'iydro'g'ensulfide)were-discharged. The liquid product, consisting "of approximately 223parts, contained about 1.2 parts of a brown 'oil. The remainder, anaqueous 'sdhitio'n, "distilled under diminished pressure giving 34.2parts of propionamide. The yield'of amide was "59 based on the weight ofpropylene introduced inpre'pa'r ing the propylene-sulfur oil, and theyield, "based on the amount of propylene' sulfur-oil employed, was 66%.

Emample -2. -In the same as "in E2:- ample 1, a propylene-sulfur 011containing 6-? 795 sulfur and corresponding to an average composition of(C3H7)='2S5.7 was prepared in 25% yield, based upon the weightoflpropylene, by heating a mixture of the following ingredients for onehour at 170-185 0.:

Parts Water (2.5 mols) l llnshaflosilsamaei 45 1,a-propylene-sulfunoil'containiiig'63.5% siilf'ur Y and corresponding toan "average composition off (CriH7)2S4'.7 was prepared In 6915%Iyild,based upon the weight'of propylene, by heating a-mixture of thefollowing ingredients at 195-202 C. for 30 minutes.

Cobalt sulfide 7.5 parts} mixed to form Waterm. 36. 5 parts a slurryWater (2.25 mo1s) 40.5 parts Hydrogen sulfide (1.38 mols) 47 partsSulfur dioxide (0.50 mol)... 2 parts Propylene (0.75 mol) 31. 5 partsThe propylene-sulfur oil produced above was converted to propionamide(11.9% yield, based on the weight of propylene) by heating a mix- "tureof 47:6 parts (0.202 mol) of the propylenesulfur oil, 19 parts (1.06mols) of water, and 9 parts (053 mol) of ammonia at 250-275" C. for 15minutes.

-Eztample 4.In a manner similar to Example 1, the following ingredientswere heated at 205-225 C. for 15 minutes to produce a propylene-sulfuroil containing 66.4% sulfur in 88.1% yield, based upon the weight ofpropylene:

'The resulting propylene-sulfu'r oil 'co'n'tained 64.3% sulfur, and wasformed in 893% "yield, based on the Weight of propylene.

Propionamide was prepared in 455% yield, based u on the Weight 6fpropylene, from the above propylene-sulfur oil 'by heating a miictu'r'eof 45.4.par' ts -(0I17mol') of the propylene-sulfur 6115113 parts (1.125'mols) of ammonia, and'20l3 parts (0.70 mol) of water to 240-250" C. for30 minutes.

Example "6.In a manner similar to Example 1, a propylene-suliur oilcontaining'64.7% sulfur and corresponding to an average composition of(C3H7)2S5.o was isolated in an'88.'0.% yield, based upon the weight ofpropylene, by heating at -210-C. i0r 15 minutes a mixture of the T61-lowing:

Pro'pionamide was prepared i'n about 50% yield, based upon the weight ofpropylene, from the abo-y'e propylene-'sulfur-oil by heating a mixtureof 4534 parts (0.1711101) of the propylen'esulfur oil, 1 1.0 parts (1.13mol) of ammonia, and 203 parts (0.7011101) "'01" *w'at'erto '240 250'-C. fdr B0 minute's.

'Eficzvitple 7.---In a manner similar to "Example 1, 'an ethylene-sulfuroil "containing 65.3% sulrur'and correspondingto an average compositionof (Cal-1572834 was prepared in "96.9 yield, based upon the weight ofethylene, by heating a mixture of the following ingredients at 196-200C. for 18 minutes:

Parts Ethylene (1.0 mol) 28 Trimethylamine (0.1 mol) 6 Sulfur dioxide(0.83 mol) 53 Hydrogen sulfide (2.17 mols) 74 Water (3.0 mols) 54 PartsIsobutylene (1.0 mol) -56 Trimethylamine (0.1 mol) 6 Sulfur dioxide(0.83 mol) 53 Hydrogen sulfide (2.17 mols) 74 Water (3.0 mols) 54 Theresulting isobutylene-sulfur oil was converted to isobutyramide (18.5%,based upon the weight of isobutylene) by heating a mixture of 73.3 parts(0.255 mol) of the isobutylene-sulfur oil, 27 parts (1.6 mols) ofammonia, and 29 parts (1.5 mols) of water at 260263 C. for minutes.

Example 9.In a manner similar to Example 1,

a propylene-sulfur 011 containing 73.8% sulfur and corresponding to anaverage composition of (C3I'I7)2s7.6 was prepared in 85.5% yield, basedupon the weight of propylene, by heating a mixture of the followingingredients at 200-260 C.

for 1 hour:

Parts Propylene (0.33 mol) 13.9 Trimethylamine (0.033 mol) 2 Sulfurdioxide (0.56 mol) 35.6 Hydrogen sulfide (1.44 mols) 49 Water (1.67mols) The resulting propylene-sulfur oil was converted to propionamide(44.0% yield, based upon the weight of propylene) by heating a mixtureof 43.1 parts (0.131 mol) of the propylene-sulfur oil, 8.5 parts (0.5mol) of ammonia, and 18 parts (1.0 mol) of water at 200-205 C. for 30minutes.

Example 10.-In a manner similar to Example 1, a propylene sulfur oilcontaining 31.1% sulfur and corresponding to an average composition of(CsI-Iv)2S1.2 was prepared in 69% yield, based upon the weight ofpropylene, by heating a mixture of the following ingredients at 248253C. for 1 hour: 3

Parts Propylene (0.50 mol) 21 Trimethylamine (0.50 mol) 30 Sulfurdioxide (0.56 mol) 24 Hydrogen sulfide (0.37 mol) 46 Water (1.50 mols)27 The following mixture was reacted at 240-250" C. for 30 minutes:

Parts Propylene-sulfur oil (0.15 mol) 18.6 Water (0.75 mol) 12.6 Ammonia(3.5 mols) 60 The entire liquid product was completely distilled but nopropionamide was recovered.

6 Eat-ample 11.The following materials were in troducedv into astainless steel cylindrical pressure tube:

' Parts Di-n-propyl disulfide (0.50 mol) (commercially prepared) 75Water (1.5 mols) 2 Ammonia (4.5 mols) 43 The tube was shakenmechanically for 30 minutes at a temperature between 257-265" C., andthereafter the tube was cooled to room temperature. The product was atwo-phase liquid. The

top oil layer, 60 parts, contained 35% S and cor-' responded to anaverage composition (C3H'z) 2S1.5. The aqueous layer contained aquantity of propionamide corresponding to between 2 and 3 percentconversion of the di-n-propyl disulfide.

As illustrated in the foregoing examples, the alkene-sulfur oil may beprepared by reacting an aliphatic alkene with sulfur and hydrogensulfide or with sulfur dioxide and hydrogen sulfide. The reactions maybe carried out in a medium consisting of the essential reactants, asillustrated in Examples 5 and 6, or in an aqueous medium or in asuitable solvent such as dioxane, pyridine or benzene under anhydrousconditions. When elemental sulfur is reacted with an alkene, addition ofhydrogen sulfide to the reactants facilitates initiation of thereaction, but initial addition of hydrogen sulfide is not necessary.Usually about 1 mol of hydrogen sulfide per 2 mols of alkene is usedwhen elemental sulfur is a reactant; and when sulfur dioxide andhydrogen sulfide are used, about 2 mols of hydrogen sulfide per mol ofalkene is employed.

Suificient sulfur or sulfur dioxide must be reacted with the alkene toproduce an alkene-sulfur oil containing sufficient combined sulfur, e.g., polysulfide sulfur, to have at least an average composition(CnH2n+1) 2S3, preferably The average composition of the alkene-sulfuroil is based upon the sulfur analysis, as illustrated in the examples.Since the alkene is completely converted to oil the amount of carbon andhydrogen present was assumed to be equal to that represented by thealkene charge. A complete analysis was run on the oil produced inExample 1, and this verified the fact that the average composition ofthe alkene-sulfur oil could be accurately determined from the sulfuranalysis.

Example 10 illustrates that no yield of amide is obtained upon reactingan alkene-sulfuroil having an average composition (CnH2n+1)2S1.2. From apractical standpoint the average composition should be betweenpreferably (CnH2n+1) 285. From the standpoint of converting the oil toamide no particular advantage is obtained in preparing an oil having asulfur content greater than Se.

Example 1 gives a typical analysis of the general composition of thealkene-sulfur oils employed in the present process. As shown, only smallamounts of mercaptans are formed and this appears to be a maximum. Ingeneral, the amount of mercaptans formed is less than about 0.5%.Furthermore, only small amounts of monoand di-sulfides are formed, andthe alkene-sulfur oils essentially consist of alkyl trisulfides andhigher sulfides. In preparing the oils, at least 5 mols of sulfur arenecessary to convert 2 mols of an alkene to an alkene-sulfur oilFsufiicient Ito be unable. of being converted: to amide Zhy;:r eacting'with sammonia or an aliphatic primary or secondary amine. In general, atleast about 0.6-0.7 mol of sulfur .dioxide perunolof alheneis employed.in reactions. involving .sulfur -dioxide emd chydrogen sulfide.

*In-the .preparation..oialkeneesulim' OilS'fby freacting .an. alkenewithsulfuredioxide andhydrogen sulfide, .it is .to'. beunderstoodthatacatalytic amount of -an aliphatic tertiarvamine .or .metal sulfide from.the group consisting of -.cobalt, nickel, .zinc and manganese should beadded t thereactants. .Suitable aliphatictertiaryamines aretrimethy'lamine, .tr'iethylamine, jtripropylamines and tribntylamines.The metal. sulfides are usuallyintroduced into the reactioniin theformbf an .aqueous .slurry .as illustrated in TEX- amplei3. .Onlyrelatively smallamounts of these catalytic materials are used,'this".being about 1 %.'-5 based upon the .total weight of reactioncomponents. Little .or noyield of ,alkene-sulfur oil isobtainedin .theabsence of these. catalytic materials.

.In the preparationofthe alkene sulfur oil, the rate of reactionistoolowito. bepractical at temperatures -appreciablyibelow. 160 1C.-Prolonged exposure.of.the.alkeneesulfureilsltotemperatures above 250..C.-. results in. decomposition. The. preferred temperature is between190C- an'di21'0'C. In theconizersion ,of oil to. amide practicalreaction rates .are obtained at a temperatureaof 115 C. .andabove.Temperatures in excess of 350 .10. .result .in decomposition of theamide product. The preferredtemperature is between2,4.0"..C..and.270"'.C.

.Theconversionof alkene-sulfur oil .to. amide may be carried out in-anaqueous medium .or underanhydrous conditionsflin; an ,inert. solvent.Satisfactory solvents i include .d-ioxane, pyridine and benzene. Whensubstantially anhydrousconclitions prevail, the alkanoic acid amide is athicamide :.,containing .the. group C.SN,R2 "where :R is. hydrogenoran-alkyl radical. When .water is present, the correspondinramidecontains-the group-CONRz where .R is hydrogenoralkil.Theoretically, .2 mols .of. ammonia :or an aliphatic primary orsecondary .amine are required to .react with 1 vmol. of vthealkene-sulfur. .oil, the molecular. weight cf. the alkene=suliiur oil.being. based upon the average composition. Furthermore, when aqueousmedium .is used,:2 mols of waterare .theoretically required to-reaet.with 1 mol .of :the .alkeneesultur .oil. Anexcess .of water and.ammonia oramine. are preferred, .however, and. usually..& mols of.wa-ter .permol ..of alkenesulfur oil, and about 5 mols of.amrnen.ia;p.er..mol of alkene-sulfur oil are employed. Excessive amounts of watertend to hydrolyze'the resulting amide. in .general,. it shouldbeunderstood: that the proportionsiof reactants maybesvaiiedinithesecondzstep of the presentprocess, .as the reaction will take place inthe presenceiof any appreciable amounts of the reactanta'merQy -the rateof the reaction and'thewapproach of theyield to theoretical-beingafiectedias proportions are-varied.

Various aliphatic primary and cseoondary amines-which maybe-used include:methylam-ine, ethylamine, :propylam-ines, {and butylamines.

, Since elevated temperatures .are required in preparing-thealk-ene-sulfur oil :and in" the 3.001 version of roiltosamines, thereactions are .carried out in a closed system to avoid loss.ofrroactants fromathe-reaetion. medium by vaporization. Consequently,the :absence ':'of cappliedmres- 8 sure, the pressune :of :the: system.will :iraty with the temperature of the reaction and thevolatility .of:the reactants or the reaction medium.

:Lclaim:

1. Aprocess. forpreparingelkanoic acid amides which comprises heatingzan -:alkene sulf.ur .oil of .thecomposition .(Cn'H2n+1)2Se, wherein a:hasa walue. of .at .least..3, .with .water and a. nitrogen-.containingcompound from thegroup consisting .of.ammonia, aliphaticprimary amines, and aliphatic-secondary amines, asthe sole reactants, ata temperature Withinthe range C. .and 350 C. whereby an alkanoic acidamide is'produced, and thereafter separating thesaid alkanoic acid amide.irom Y the/resulting. mixture.

2 ;The,process of-elaim. l 2 wherein. the alkenevsillfiur .oil. is anoilwwhichisproducedby reaction between an alkeneeand .suliur'at atemperature "within therangeof. -160-.Caand .250" C.

.3. .llhaprowss 10f .claim -:1 wherein the said alkene-sulfur oil isan..oil obtained-by-reaction between an alkene and sulfur in thepresence of hydrogen sulfide at a temperature -with-in :the range of 190C. and 210 .0.

4. The process of claim .l-wherein'x has a. Malue .of from 3 to 8inclusive and .w-hasa-value of from .2 to 4, the alkene-sulfur oilbeingthe oil-obtained by reaction between an alkene, containingfrom2--to4 carbon atoms, *a-nd'sulf-ur "in the presence of "hydrogen sulfideat a temperature wit-hinthe range of "190 Cflto 210C.

"5. The, process "of claim l wherein thealkenesulfur'oilgis the oilwhich is obtained 'by' heating 'an alkene anda mixture of sulfur dioxideand hydmg-en "sulfide-in{the-"presence of a-catalytic quantity of' an*aliphatic tertiary amine.

- GJ'TTheprOcess of claim hwhere'in th alkenesulfur oi-l'jis the oilobtained by reactionbetween anialkenearidamiature of sulfur dioxide andhydrogen sulfide in-the presence eta-catalyst from the group consistingof cobalt, nickel, zine-and manganese sulfides.

"7. The -process of claim "wherein the said alkene-sulfu-r -oil-isprepared 'at a temperature within therange of 1-60 Cr-and '250" .0.

P8. The -process *of claim -6 wherein the :sai alk-ene-su-lfur *oil isprepared at a temperature withinnthe :raneeof -;190 v.C.- wand ;-.21.0

'-9- A p o ss i rennem in spnomonamidewhich m ni e hetdneaz.mlysulfide-ciror theiformula (Gal-I1)=2S.=wvherein;:x.:has.a:va-luetof '-f12om;:3 torzB ainolusive, .wit-h Jam water :at 38'perature within: the ra ezof .1175". C. and-2350*- 10., withoutadditional v:f ree 101' -:combined .-.-s.ultur, whereby the woisulfideoi l,awater and amm nia-reactito produce wonionamide;.-andthereafter. separating.zthesaidpmgpionamide from the resul ing rea ti nmixture.

.ropn :proeess .tor mreaaring -imonionamide which consists essentiallyin heating a:polysulflde flilaiof the formula (C3H'1)2sz, wherein a: hasa value of from ,3 to 8.inclusive-withammoniaand wa er. at a mprature-within? h ran e ot240 .C. to 270 (1., wherebythe,.;pQl/'.S\11.fide,-oil,qwatcr, fend ammonia react qpuoduee,rmpi-onamideand thereafter separating the said propionamide trom theresulting reaction mixture.

11;"1heprocess of claim '10 wherein -the 'said polysulfide oil is theoil whiclris obtained. by reaction between,propylene, .sulfur dioxideand hydrogen sulfide in the presence of trimethyl- Shaina-"catalyst "ata "temperature of "190 C. to

ldmmea ztor manning acetamide which comprisdsihflflrtingzmnelib'yleneesulfurg oilooif 9 composition (Cam-328$, wherein a: has avalue of at least 3, with ammonia, and water at a temperature within therange of 175 C. and 350 C., whereby acetamide is produced, andthereafter separating the said acetamide from the resulting reactionmixture.

13. A process for producing isobutyramide which comprises heating anisobutylene-sulfur oil of the composition (Cd-Io) ZSr, wherein a: has avalue of at least 3, with ammonia and water at a temperature within therange of 175 C. and 350 0., whereby isobutyramide is produced, andthereafter separating the said isobutyramide from the resulting reactionmixture.

14. The process of claim 13 wherein the said 15 2,495,567

HARRY A. STRAW.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,051,806 Allen Aug. 25, 1936 2,459,706 King Jan. 18, 1949Carmack Jan. 24, 1950

1. A PROCESS FOR PREPARING ALKANOIC ACID AMIDES WHICH COMPRISES HEATINGAN ALKENE-SULFUR OIL OF THE COMPOSITION (CMH2N+1)2SR, WHEREIN X HAS AVALUE OF AT LEAST 3, WITH WATER AND A NITROGENCONTAINING COMPOUND FROMTHE GROUP CONSISTING OF AMMONIA, ALIPHATIC PRIMARY AMINES, AND ALIPHATICSECONDARY AMINES, AS THE SOLE REACTANTS, AT A TEMPERATURE WITHIN THERANGE 175/ C. AND 350* C. WHEREY AN ALKANOIC ACID AMIDE IS PRODUCED, ANDTHEREAFTER SEPARATING THE SAID ALKANOIC ACID AMIDE FROM THE RESULTINGMIXTURE.